Enhanced autophagic flux contributes to cardioprotection of remifentanil postconditioning after hypoxia/reoxygenation injury in H9c2 cardiomyocytes

Abstract

Remifentanil postconditioning (RPC) has been shown to provide potent cardioprotection against ischemia/reperfusion (I/R) injury, but the underlying mechanism has not been fully elucidated. The current study was designed to investigate whether RPC protects cardiomyocytes against I/R injury through enhancement of autophagic flux. H9c2 cardiomyocytes were exposed to hypoxia/reoxygenation (H/R) to mimic myocardial I/R injury in vitro. Autophagosome formation was evaluated by detecting of light chain 3 (LC3) puncta number and LC3Ⅱ levels using immunofluorescence and western blotting, respectively. Additionally, dual fluorescent staining of LC3 and lysosomal-associated membrane protein 2, a lysosomal marker protein, were used to detect autolysosome formation. Moreover, autophagic flux integrity was tracked using changes in LC3Ⅱ and p62 levels. Lastly, myocardial injury was detected by Hoechst 33342 and propidium iodide staining and MTT assay. The results showed that RPC increased autophagosome formation and promoted autophagosome-lysosome fusion, thereby improving autophagic flux in H9c2 cells. Reversal of these effect by bafilomycin A1 or chloroquine co-administration at reoxygenation onset indicated that RPC improved the impaired autophagic flux following H/R injury. Induction of autophagy was associated with increased cell viability and decreased apoptosis. Autophagy inhibition with bafilomycin A1 or chloroquine and ATG7shRNA significantly abolished RPC-induced cardioprotection. In conclusion, our finding that RPC can protect cardiomyocytes against H/R injury through enhancement of autophagic flux suggests a new mechanism for myocardial protection of opioid postconditioning.